Silylation of surfaces has been practiced extensively since the early 1950's. U.S. Pat. No. 2,722,504 to Fleck described methods for improving the organophilicity of catalysts and adsorbents by treating with compounds of the general type R.sub.1 R.sub.2 R.sub.3 SiX where R.sub.1 R.sub.2 and R.sub.3 may be organic non-hydrolyzable moieties and x is a hydrolyzable group including halogens, alkoxy and other groups which separate from silicon in the presence of water. Though Fleck did not describe the reaction, the surface hydroxyls of insulating surfaces like silica, alumina, magnesia and zeolites, may interact with such silanes in the following way: ##STR1## (s) denotes a surface silicon Many variations on this reaction with other silicon reagents and other surfaces but particularly silica have been studied, see: "Study of the Surface and Bulk Hydroxyl Groups of Silica by Infra-red Spectra and D.sub.2 O Exchange", Kiselev et al, Trans. Farad. Soc. 60, 2254 (1964); "Reactions of Chlorosilanes with Silica Surfaces" Hair et al., J. Phys. Chem. 73 #7, 2372 July 1969; "Reactions of Chloromethyl Silanes with Hydrated Aerosil Silicas" Armestead et al., Trans. Farad. Soc. 63, 2549 (1967); "Adsorption and Reaction of Methylchlorosilanes at an `Aerosil` Surface" Evans et al., J. Catalysis 11, 336-341 (1968).
More recently, patents have been issued pertaining to the reactions of organosilanes with zeolites and the subsequent benefits of this treatment.
U.S. Pat. No. 3,682,996 issued to Kerr claims a zeolite ester product (more properly described as a silicon ether) derived from the reaction between a silane containing an available hydrogen atom and an aluminosilicate zeolite. ##STR2## where x is between 1 and 4 and where R is independently at least one organic radical, suitably aryl, alkyl, acyl, aralkyl but preferably alkyl because the pore structure will more readily accept alkylsilanes than arylsilanes. Apart from these classes of silanes Kerr makes a reference to one other silane not fitting this formula, hexamethyl disilazane. Kerr does not disclose or claim usage of halosubstituted silanes.
The reactions described by Kerr all occur under vacuum conditions wherein the outgassed H form zeolite is contacted with pure organosilane vapor or liquid at various temperatures. Kerr discloses, but does not demonstrate or claim, that the silylated zeolite may be used in catalytic applications, including "certain shape selective catalyzed reactions".
U.S. Pat. No. 3,726,309 to Allum claims a product derived from the reaction of an inorganic material containing hydroxyl groups, including aluminosilicates, modified by treatment with an organic radical substituted silane. Bound silicon ethers are formed by reaction with the surface hydroxyl groups.
U.S. Pat. No. 3,658,696 to Shively claims an improved separation process resulting from the reactions of zeolite molecular sieves with organosilanes. The replacement of OH radicals on the zeolite surface with silane radicals significantly affects the surface adsorption properties of the molecular sieve because the hydroxyl groups are the main centers of surface adsorption. In this instance bulky silanes were chosen which reacted with only the external surface of the zeolite.
Zhomov et al., Katal, Pererab, Uylevodorad, Syr'ya 1968 (2) 9 (from Ref. Zh. Khim 1969 abstract No. 4N196) used a methyl chlorosilane to change the properties of an aluminosilicate used to alkylate phenol with a tetrameric propylene.
U.S. Pat. No. 3,980,586 to Mitchell claims a new product resulting from a sequence of silylation, calcination and steaming of a group of materials consisting of alumina, silica alumina and aluminosilicates. Calcining continues for a sufficient time and at high enough temperatures to remove all of any introduced organic or halogen substituent (unlike Kerr, Mitchell has used a more general form of silanes which includes halogens). The amount of silane used was sufficient to achieve about 1-5% of a new SiO.sub.2 layer. U.S. Pat. No. 4,080,284 to Mitchell claims the new materials to be useful for catalytic hydroconversion.
U.S. Pat. No. 4,002,697 to Chen used a silane treatment on ZSM-5 to improve the yield of p-xylene from methylation of toluene. In this instance the silane was chosen so as to interact only with the external surface.
U.S. Pat. No. 3,698,157 and U.S. Pat. No. 3,724,170 to Allen demonstrated that improved separation of C.sub.8 aromatics could be achieved by contacting alumino-silicate adsorbents with organic radical or halo substituted silanes.